The Old Fort Point Formation of the Jasper anticlinorium comprises some 1200 feet of argillite, siltstone, limestone, and limestone-breccia, probably Precambrian in age. The sequence, divided into four members, probably records the westward migration of an ancient delta. Member A, the oldest, displays some 350 feet of argillaceous bottomset beds, while the overlying 500 feet of member B strata represent the foreset beds, characterized by numerous lenses of intraformational limestone-breccia. A break in the orderly sequence of events is recorded by the several hundred feet of homogeneous argillite of member C. However the 150 feet of silty argillite and siltstone of member D, overlain conformably by sandstone and quartz pebble conglomerate of the Miette Formation probably represents the final phase of the transition from fairly deep water, to very shallow water deposition.
These rocks were tightly folded into a series of overturned anticlines and synclines, comprising the Jasper anticlinorium, and elevated to their present structural position by movement along the Pyramid thrust-fault during the Laramide orogeny. Flow-cleavage, fracture-cleavage, and cleavage-boudinage are well developed and excellently exposed. Nine joint-sets record the complicated nature of local stress systems throughout the tectonic history of the anticlinorium.
Observed mineral assemblages are typical of the quartz-albite-muscovite-chlorite subfacies of the greenschist facies. These minerals appear to have been in stable equilibrium with calcite, indicating very low grade regional metamorphism in the presence of a relatively high carbon dioxide partial pressure.